Environmental air pollution.

The effects of air pollution on health have been recognized for many hundreds of years. In London, during December 1952, a particularly bad smog, which involved extreme elevations of both SO 2 and black smoke, was associated with more than 1,000 extra deaths during a 5-d period (1). The majority of the pollution responsible for smogs is derived from the domestic and industrial burning of fossil fuels. The introduction of legislation to reduce the burning of fossil fuels in Britain and elsewhere has meant that the make-up of environmental air pollution has changed considerably. However, the decline in fossil fuel-associated pollutants has been replaced by a steady increase in traffic-associated pollutants such as finer, respirable particulates, oxides of nitrogen (NOx), ozone (O 3 ), and volatile organic compounds (VOCs).